Re: [Qemu-devel] [Qemu-ppc] [PATCH 1/7] pci: add MPC105 PCI host bridge emulation

[Andreas Färber]

Am 06.05.2013 22:57, schrieb Hervé Poussineau:
> Alexander Graf a écrit :
>> On 05/03/2013 07:57 AM, Hervé Poussineau wrote:
>>> Alexander Graf a écrit :
>>>>
>>>> Am 02.05.2013 um 22:08 schrieb Hervé Poussineau <address@hidden>:
>>>>
>>>>> Non-contiguous I/O is not implemented.
>>>>>
>>>>> There is also somewhere a bug in the memory controller, which means
>>>>> that some real firmwares may not detect the correct amount of memory.
>>>>> This can be bypassed by adding '-m 1G' on the command line.
>>>>>
>>>>> Add x-auto-conf property, to automatically configure the memory
>>>>> controller at startup. This will be required by OpenBIOS, which
>>>>> doesn't know how to do it.
>>>>
>>>> Why not teach it? I'd prefer to see that logic in firmware.
>>>
>>> Me too, but I'm not confident enough in my capabilities to do it.
>>
>> Huh? Why not? Most of the device initialization code in OpenBIOS
>> happens in C, so you don't even have to touch Forth code :).
>>
>>> Autoconfiguration is only in one place of the code, so I think it can
>>> be removed easily once OpenBIOS has this logic.
>>
>> I'd prefer if we could come up with a clean model from the start. It
>> really shouldn't be hard at all.
>>
> 
> I thought that for all other usages of OpenBIOS in QEMU, RAM was
> supposed to be available as soon as machine was powered on.
> 
> However, I checked OpenBIOS code:
> One of the first things done in arch/ppc/qemu/start.S is to copy the
> exception vectors. So, I should add code before it to detect memory
> controller, detect ram size and configure memory controller?

No. Why? QEMU does not depend on the memory controller being
initialized, only the OS might expect some registers to be filled in. So
you should look at or add the MPC105 PHB initialization hook in
OpenBIOS' PCI code, long after the memory is set up.

> It seems quite a bit of code.
> Do you have an example of how to do it for another memory controller, so
> I can adapt the code?

Not sure if there's a memory controller specifically, but the Mac PHBs
are being initialized and on my PReP OpenBIOS branch I may have touched
that code...

Regards,
Andreas

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